WASHINGTON, D.C.--When a whale dies, its carcass sinks to the sea floor, where it provides food for a unique assemblage of worms, clams, mussels and other creatures. But commercial whaling is driving many of these species to extinction, according to new results presented here today at the annual AAAS meeting.
The deep-ocean floor is dark and cold, and most creatures there rely on food that falls from above. Nothing provides a greater feast than the carcass of a great whale, which can deposit up to 160 tons of blubber, meat and bone in one fell swoop. In 1987, while surveying a region of sea floor in the submersible Alvin, Craig Smith of the University of Hawaii, Manoa, stumbled on an entire community of animals thriving on and near a submerged whale skeleton. Since then, he and other researchers have shown that these "whale falls," like hydrothermal vents and cold seeps, constitute a unique biological community (ScienceNOW, 30 July ).
To estimate how 2 centuries of commercial whaling has affected these communities, Smith and colleagues combined whale-population estimates with standard ecological models that link habitat loss to biodiversity. The models predict that in the North Atlantic, where at least 75% fewer whale corpses are littering the deep since large-scale whaling began in the early 1800s, between 30% and 50% of species that depended on whale carcasses have already gone extinct. And worldwide, even the so-called sustainable levels of whaling recommended by the International Whaling Commission will cause 15% of whale-fall species to disappear forever.
"It's absolutely fascinating" work, says biological oceanographer Steven Palumbi of Stanford University: It demonstrates that human activity can affect entire marine ecosystems that are completely unknown.